1. a The Centre for Research on Drugs and Health Behaviour , Charing Cross and Westminster Medical School, University of London
2. b MRC Sociology Unit , Glasgow
3. c Communicable Diseases (Scotland) Unit Ruchill , Hospital , Glasgow
4. d Department of Infection and Tropical Medicine , Ruchill Hospital , Glasgow
5. e Public Health Research Unit , Glasgow University
6. f The Public Health Laboratory Service, Colindale , London , UK